The weft threads are supplied from supply spools in shuttleless looms operating with weft insertion and withdrawal gripper rods. The particular weft thread presently to be inserted is selected by a special weft selector device for presentation to the gripper of the gripper rod in such a position that the gripper can seize the thread for insertion into the loom shed. The weft selector device includes a weft presenting needle for each of the individual weft thread pulled off the supply spools. These needles have a needle eye at their free ends for holding the respective weft thread. The thread presenting needles are moved from a rest position into a work position and back again, whereby the work position is specific for each weft presenting needle yet enabling the seizing of the thread by the gripper. Several constructions of the just described mechanism are known in the art. However, for present purposes only those mechanisms are relevant for the weft thread selection and presentation in which the weft threads are guided and presented by linearly displaceable weft presenting needles. U.S. Pat. No. 4,785,856 (Gehring et al.) discloses an apparatus for presenting weft threads to a gripper in shuttleless looms. U.S. Pat. (Gehring et al.) is based on German Patent (DE-PS) 3,618,445. In the known device weft threads are presented to a gripper by needles, each of which is guided by at least one straight needle guide held askew in a needle guide carrier. The straight needle guides due to their askew arrangement make sure that all needles together are located in and displaceable in a fan-type plane twisted in space. In the working position of each needle the respective needle eye is located on a short line extending approximately in parallel to the gripper path. Thus, all weft threads in their presenting position are close to each other in a narrow presenting zone within the reach of the gripper path for a sure transfer and gripping at the beginning of the forward gripper motion at which time the gripper speed is still slow so that the weft threads are gripped gently. The straight needle guides held askew in the at least one guide carrier form a row of guides which is slanted by a given angle relative to the gripper pass to form the fan-type plane twisted in space. A second row of askew straight guides may be arranged in a second carrier. The straight guides in the known mechanism are arranged in a section of the carrier in a row and the further straight guides are positioned in another row in a guide section of the mechanism, whereby the two rows form such an angle relative to each other that the straight guides of both rows guide the needles to be positioned in the fan-type plane twisted in space. The just described weft presenting mechanism has the advantage that the positions where the gripper can seize the presented thread are located close to each other from the first to the last weft thread available for selection so that the weft thread seizing can take place with a relatively small gripper stroke with an exact, almost point position thread presentation to the gripper of the rod. Yet, there is room for improvement, especially with regard to the exchange of the thread selecting and presenting components from loom to loom.
European Patent Publication EP 0,478,986 A1 corresponding to U.S. Pat. No. 5,172,735 (Kleiner) discloses a weft thread selecting and supplying device with an electronically controllable electric motor which drives a drive wheel which in turn drives a drive belt that is looped around the drive wheel and a guide wheel. The belt carries thread presenting needles that are driven back and forth between a ready position and a thread presenting position for the respective weft thread. The apparatus of the just mentioned European Patent Publication includes a housing in which the drive belt is driven in a slipless manner. The drive belt is looped around a drive wheel and a guide wheel having a defined diameter difference between the diameter of the drive wheel and the diameter of the guide wheel, as well as a defined on-center spacing between these wheels. Due to the different wheel diameters, straight lines that extend the respective drive belt run, intersect in a point and the weft presenting needle that is secured to each of the two drive belt runs, is moved with its needle eye into that point for presenting the weft thread to the gripper, whereby one needle is in a standby position and the other is in the thread transfer position. These positions of the needles are positively exchanged simply by rotating the drive wheel. However, the apparatus of Kleiner can also work with but one thread presenting needle connected to just one of the runs of the drive belt. In both instances, the electric motor rotates the drive wheel in accordance with a pattern being woven and in synchronism with the weaving cycle so that the drive wheel moves the drive belt accordingly. One thread presenting needle is positively positioned in the standby or in the presenting position. Two needles are repeatedly exchanged when the motor is driven in one direction or in the opposite direction.
In the device of Kleiner the electric motor can be controlled independently of the loom control to stop a weft thread supply, for example when the loom is stopped in response to the detection of a faulty warp thread or a faulty weft thread.